RACH design for beamformed communications

ABSTRACT

In a mmW network, a UE and a base station may establish a link using a RACH procedure. Because mmW and other band communications may rely on accurate beamforming to overcome link attenuation, the UE may need to provide beam information feedback to the base station. In particular, the UE may receive a beam-formed message from the base station during the RACH procedure. The UE may determine beam information based on the received beam-formed message during the RACH procedure. The UE may transmit a message to the base station during the RACH procedure, and the message may include the determined beam information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application Ser.No. 62/348,797, entitled “RACH DESIGN FOR MILLIMETER-WAVECOMMUNICATIONS” and filed on Jun. 10, 2016, which is expresslyincorporated by reference herein in its entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to random access channel (RACH) design for beamformedcommunications, such as millimeter wave (mmW) communications and othercommunications.

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is a set of enhancements to theUniversal Mobile Telecommunications System (UMTS) mobile standardpromulgated by Third Generation Partnership Project (3GPP). LTE isdesigned to support mobile broadband access through improved spectralefficiency, lowered costs, and improved services using OFDMA on thedownlink, SC-FDMA on the uplink, and multiple-input multiple-output(MIMO) antenna technology. However, as the demand for mobile broadbandaccess continues to increase, there exists a need for furtherimprovements in LTE technology. These improvements may also beapplicable to other multi-access technologies and the telecommunicationstandards that employ these technologies.

In a mmW network, a user equipment and a base station may establish alink using a RACH procedure. Because mmW communications and otherbeamformed communications may rely on accurate beamforming to overcomelink attenuation, a need exists to improve the link between the userequipment and the base station by enabling feedback of controlinformation during the RACH procedure.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In an LTE contention-based RACH procedure for uplink timesynchronization, a user equipment sends a first message and listens fora second message from a base station. In response to the received secondmessage, the user equipment sends a third message to the base station.Unlike LTE communications, mmW and other beamformed communications mayrely on accurate beamforming to overcome link attenuation. As such, in ammW network, the second message from the base station for thecontention-based RACH procedure may be transmitted using beamforming. Aneed exists to improve the link between the user equipment and the basestation by enabling feedback during the RACH procedure, such as duringthe transmission of the third message from the user equipment to thebase station.

In an aspect of the disclosure, a method, a computer-readable medium,and an apparatus are provided. The apparatus may be a user equipment.The apparatus may receive a beam-formed message from a base stationduring a RACH procedure. The apparatus may determine beam informationbased on the received beam-formed message during the RACH procedure. Theapparatus may transmit a message to the base station during the RACHprocedure that includes the determined beam information.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DLframe structure, DL channels within the DL frame structure, an UL framestructure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of an evolved Node B (eNB)and user equipment (UE) in an access network.

FIG. 4 illustrates diagrams of a mmW network.

FIG. 5 is a diagram of a modified RACH procedure for mmW communications.

FIG. 6A is a diagram of a message transmitted during a RACH procedure.

FIG. 6B is a diagram of a resource block allocated during a RACHprocedure.

FIG. 7 is a flowchart of a method of wireless communication.

FIG. 8 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 9 is a diagram illustrating an example of a hardware implementationfor an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example embodiments, the functions describedmay be implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The basestations 102 may include macro cells (high power cellular base station)and/or small cells (low power cellular base station). The macro cellsinclude eNBs. The small cells include femtocells, picocells, andmicrocells.

The base stations 102 (collectively referred to as Evolved UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access Network(E-UTRAN)) interface with the EPC 160 through backhaul links 132 (e.g.,S1 interface). In addition to other functions, the base stations 102 mayperform one or more of the following functions: transfer of user data,radio channel ciphering and deciphering, integrity protection, headercompression, mobility control functions (e.g., handover, dualconnectivity), inter-cell interference coordination, connection setupand release, load balancing, distribution for non-access stratum (NAS)messages, NAS node selection, synchronization, radio access network(RAN) sharing, multimedia broadcast multicast service (MBMS), subscriberand equipment trace, RAN information management (RIM), paging,positioning, and delivery of warning messages. The base stations 102 maycommunicate directly or indirectly (e.g., through the EPC 160) with eachother over backhaul links 134 (e.g., X2 interface). The backhaul links134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacro cells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use MIMO antennatechnology, including spatial multiplexing, beamforming, and/or transmitdiversity. The communication links may be through one or more carriers.The base stations 102/UEs 104 may use spectrum up to Y MHz (e.g., 5, 10,15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation ofup to a total of Yx MHz (x component carriers) used for transmission ineach direction. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or less carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ LTE and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing LTE in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network. LTE in an unlicensedspectrum may be referred to as LTE-unlicensed (LTE-U), licensed assistedaccess (LAA), or MuLTEfire.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMES 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService (PSS), and/or other IP services. The BM-SC 170 may providefunctions for MBMS user service provisioning and delivery. The BM-SC 170may serve as an entry point for content provider MBMS transmission, maybe used to authorize and initiate MBMS Bearer Services within a publicland mobile network (PLMN), and may be used to schedule MBMStransmissions. The MBMS Gateway 168 may be used to distribute MBMStraffic to the base stations 102 belonging to a Multicast BroadcastSingle Frequency Network (MBSFN) area broadcasting a particular service,and may be responsible for session management (start/stop) and forcollecting eMBMS related charging information.

The base station may also be referred to as a Node B, evolved Node B(eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), or some other suitableterminology. The base station 102 provides an access point to the EPC160 for a UE 104. Examples of UEs 104 include a cellular phone, a smartphone, a session initiation protocol (SIP) phone, a laptop, a personaldigital assistant (PDA), a satellite radio, a global positioning system,a multimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a smart device, a wearabledevice, or any other similar functioning device. The UE 104 may also bereferred to as a station, a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 may beconfigured to provide beam information feedback during a RACH procedure(198).

FIG. 2A is a diagram 200 illustrating an example of a DL frame structurein LTE. FIG. 2B is a diagram 230 illustrating an example of channelswithin the DL frame structure in LTE. FIG. 2C is a diagram 250illustrating an example of an UL frame structure in LTE. FIG. 2D is adiagram 280 illustrating an example of channels within the UL framestructure in LTE. Other wireless communication technologies may have adifferent frame structure and/or different channels. In LTE, a frame (10ms) may be divided into 10 equally sized subframes. Each subframe mayinclude two consecutive time slots. A resource grid may be used torepresent the two time slots, each time slot including one or more timeconcurrent resource blocks (RBs) (also referred to as physical RBs(PRBs)). The resource grid is divided into multiple resource elements(REs). In LTE, for a normal cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 7 consecutive symbols (for DL,OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a totalof 84 REs. For an extended cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 6 consecutive symbols in thetime domain, for a total of 72 REs. The number of bits carried by eachRE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot)signals (DL-RS) for channel estimation at the UE. The DL-RS may includecell-specific reference signals (CRS) (also sometimes called common RS),UE-specific reference signals (UE-RS), and channel state informationreference signals (CSI-RS). FIG. 2A illustrates CRS for antenna ports 0,1, 2, and 3 (indicated as R₀, R₀, R₂, and R₃, respectively), UE-RS forantenna port 5 (indicated as R₅), and CSI-RS for antenna port 15(indicated as R). FIG. 2B illustrates an example of various channelswithin a DL subframe of a frame. The physical control format indicatorchannel (PCFICH) is within symbol 0 of slot 0, and carries a controlformat indicator (CFI) that indicates whether the physical downlinkcontrol channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustratesa PDCCH that occupies 3 symbols). The PDCCH carries downlink controlinformation (DCI) within one or more control channel elements (CCEs),each CCE including nine RE groups (REGs), each REG including fourconsecutive REs in an OFDM symbol. A UE may be configured with aUE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCHmay have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subsetincluding one RB pair). The physical hybrid automatic repeat request(ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0and carries the HARQ indicator (HI) that indicates HARQ acknowledgement(ACK)/negative ACK (HACK) feedback based on the physical uplink sharedchannel (PUSCH). The primary synchronization channel (PSCH) is withinsymbol 6 of slot 0 within subframes 0 and 5 of a frame, and carries aprimary synchronization signal (PSS) that is used by a UE to determinesubframe timing and a physical layer identity. The secondarysynchronization channel (SSCH) is within symbol 5 of slot 0 withinsubframes 0 and 5 of a frame, and carries a secondary synchronizationsignal (SSS) that is used by a UE to determine a physical layer cellidentity group number. Based on the physical layer identity and thephysical layer cell identity group number, the UE can determine aphysical cell identifier (PCI). Based on the PCI, the UE can determinethe locations of the aforementioned DL-RS. The physical broadcastchannel (PBCH) is within symbols 0, 1, 2, 3 of slot 1 of subframe 0 of aframe, and carries a master information block (MIB). The MIB provides anumber of RBs in the DL system bandwidth, a PHICH configuration, and asystem frame number (SFN). The physical downlink shared channel (PDSCH)carries user data, broadcast system information not transmitted throughthe PBCH such as system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation referencesignals (DM-RS) for channel estimation at the eNB. The UE mayadditionally transmit sounding reference signals (SRS) in the lastsymbol of a subframe. The SRS may have a comb structure, and a UE maytransmit SRS on one of the combs. The SRS may be used by an eNB forchannel quality estimation to enable frequency-dependent scheduling onthe UL. FIG. 2D illustrates an example of various channels within an ULsubframe of a frame. A physical random access channel (PRACH) may bewithin one or more subframes within a frame based on the PRACHconfiguration. The PRACH may include six consecutive RB pairs within asubframe. The PRACH allows the UE to perform initial system access andachieve UL synchronization. A physical uplink control channel (PUCCH)may be located on edges of the UL system bandwidth. The PUCCH carriesuplink control information (UCI), such as scheduling requests, a channelquality indicator (CQI), a precoding matrix indicator (PMI), a rankindicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, andmay additionally be used to carry a buffer status report (BSR), a powerheadroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of an eNB 310 in communication with a UE 350in an access network. In the DL, IP packets from the EPC 160 may beprovided to a controller/processor 375. The controller/processor 375implements layer 3 and layer 2 functionality. Layer 3 includes a radioresource control (RRC) layer, and layer 2 includes a packet dataconvergence protocol (PDCP) layer, a radio link control (RLC) layer, anda medium access control (MAC) layer. The controller/processor 375provides RRC layer functionality associated with broadcasting of systeminformation (e.g., MIB, SIBs), RRC connection control (e.g., RRCconnection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter radio access technology(RAT) mobility, and measurement configuration for UE measurementreporting; PDCP layer functionality associated with headercompression/decompression, security (ciphering, deciphering, integrityprotection, integrity verification), and handover support functions; RLClayer functionality associated with the transfer of upper layer packetdata units (PDUs), error correction through ARQ, concatenation,segmentation, and reassembly of RLC service data units (SDUs),re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto transport blocks(TBs), demultiplexing of MAC SDUs from TBs, scheduling informationreporting, error correction through HARQ, priority handling, and logicalchannel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe eNB 310. These soft decisions may be based on channel estimatescomputed by the channel estimator 358. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 310 on the physical channel. Thedata and control signals are then provided to the controller/processor359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the eNB 310, the controller/processor 359 provides RRClayer functionality associated with system information (e.g., MIB, SIBs)acquisition, RRC connections, and measurement reporting; PDCP layerfunctionality associated with header compression/decompression, andsecurity (ciphering, deciphering, integrity protection, integrityverification); RLC layer functionality associated with the transfer ofupper layer PDUs, error correction through ARQ, concatenation,segmentation, and reassembly of RLC SDUs, re-segmentation of RLC dataPDUs, and reordering of RLC data PDUs; and MAC layer functionalityassociated with mapping between logical channels and transport channels,multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs,scheduling information reporting, error correction through HARQ,priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the eNB 310 may be used by the TXprocessor 368 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 368 may be provided to different antenna 352 viaseparate transmitters 354TX. Each transmitter 354TX may modulate an RFcarrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 310 in a manner similar tothat described in connection with the receiver function at the UE 350.Each receiver 318RX receives a signal through its respective antenna320. Each receiver 318RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

FIG. 4 illustrates diagrams 400, 450 of a mmW network. In the diagram400, for example, the mmW network includes a mmW base station 410 and anumber of UEs 420, 430. The base station 410 may include hardware forperforming analog and/or digital beamforming. If the base station 410 isequipped with analog beamforming, at any one time, the base station 410may transmit or receive a signal in only one direction. If the basestation 410 is equipped with digital beamforming, the base station 410may concurrently transmit multiple signals in multiple directions or mayreceive multiple signals concurrently in multiple directions. Further,the UE 420, for example, may include hardware for performing analogand/or digital beamforming. If the UE 420 is equipped with analogbeamforming, at any one time, the UE 420 may transmit or receive asignal in only one direction. If the UE 420 is equipped with digitalbeamforming, the UE 420 may concurrently transmit multiple signals inmultiple directions or may concurrently receive multiple signals inmultiple directions.

Extremely high frequency (EHF) is part of the RF in the electromagneticspectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between1 millimeter and 10 millimeters. Radio waves in the band may be referredto as a millimeter wave. Near mmW may extend down to a frequency of 3GHz with a wavelength of 100 millimeters (the super high frequency (SHF)band extends between 3 GHz and 30 GHz, also referred to as centimeterwave). While the disclosure herein refers to mmWs, it should beunderstood that the disclosure also applies to near mmWs. Further, whilethe disclosure herein refers to mmW base stations, it should beunderstood that the disclosure also applies to near mmW base stations.

In order to build a useful communication network in the millimeterwavelength spectrum, a beamforming technique may be used to compensatefor path loss. Beamforming technique focuses the RF energy into a narrowdirection to allow the RF beam to propagate farther in that direction.Using the beamforming technique, non-line of sight (NLOS) RFcommunication in the millimeter wavelength spectrum may rely onreflection and/or diffraction of the beams to reach the UE. If thedirection becomes blocked, either because of UE movement or changes inthe environment (e.g., obstacles, humidity, rain, etc.), the beam maynot be able to reach the UE. Thus, in order to ensure that the UE hascontinuous, seamless coverage, multiple beams in as many differentdirection as possible may be available. In an aspect, the beamformingtechnique may require that the mmW base stations and the UEs transmitand receive in a direction that allows the most RF energy to becollected.

In the mmW network, UEs may perform beam sweeps with mmW base stationswithin range. The beam sweeps may be performed as illustrated in thediagram 400 and/or diagram 450. Referring to the diagram 400, in a beamsweep, the mmW base station 410 may transmit m beams in a plurality ofdifferent spatial directions. The UE 420 listens/scans for the beamtransmissions from the mmW base station 410 in n different receivespatial directions. When listening/scanning for the beam transmissions,the UE 420 may listen/scan for the beam sweep transmission from the mmWbase station 410 m times in each of the n different receive spatialdirections (a total of m*n scans). In another configuration, referringto the diagram 450, in a beam sweep, the UE 420 may transmit n beams ina plurality of different spatial directions. The mmW base station 410listens/scans for the beam transmissions from the UE 420 in m differentreceive spatial directions. When listening/scanning for the beamtransmissions, the mmW base station 410 may listen/scan for the beamsweep transmission from the UE 420 n times in each of the m differentreceive spatial directions (a total of m*n scans).

Based on the performed beam sweeps, the UEs and/or the mmW base stationsdetermine a channel quality associated with the performed beam sweeps.For example, if the beam sweep process in diagram 400 is performed, theUE 420 may determine the channel quality associated with the performedbeam sweeps. However, if the beam sweep process in the diagram 450 isperformed, the mmW base station 410 may determine the channel qualityassociated with the performed beam sweeps. If the UE 420 determines achannel quality associated with the performed beam sweeps, the UE 420may, in on aspect, send the channel quality information (also referredto as beam sweep result information) to an anchor node 415. The anchornode 415 may be an mmW base station, an eNB, or another type of basestation. The UE 420 may send the beam sweep result information directlyto the anchor node 415 if the anchor node 415 is in range, or may sendthe beam sweep result information to a serving mmW base station (e.g.,the mmW base station 410), which forwards the beam sweep resultinformation to the anchor node 415. If the mmW base station 410determines a channel quality associated with the performed beam sweeps,the mmW base station 410 sends the beam sweep result information to theanchor node 415. In another aspect, the UE 420 may send the beam sweetresult information to the mmW base station 410. In an aspect, thechannel quality may be affected by a variety of factors. The factorsinclude movement of the UE 420 along a path or due to rotation (e.g., auser holding and rotating the UE 420), movement along a path behindobstacles or within particular environmental conditions (e.g.,obstacles, rain, humidity). The UE 420, the mmW base station 410, andthe anchor node 415 may also exchange other information, such asconfiguration information, for beamforming (e.g., analog or digitalbeamforming capabilities, beamforming type, timing information, etc.)Based on the received information, the anchor node 415 may providebeamforming configuration information to the mmW base station 410 and/orthe UE 420 (e.g., mmW network access configuration information,information for adjusting beam sweeping periodicity, informationregarding overlapping coverage for predicting a handoff to another basestation, such as a mmW base station).

In an LTE network, a UE may initiate a RACH procedure for initialnetwork access. Because the UE may not be connected to the network, theUE may not have allocated resources available to inform the networkabout its desire to connect. Instead, the UE may send a request over ashared medium—the RACH. Other UEs that are also not connected to thenetwork may also wish to send a request over the RACH for initialnetwork access. With multiple UEs transmitting over the shared resource,there is a possibility that different requests may collide. Such arandom access procedure may be referred to as a contention-based RACHprocedure. In another scenario, the network may indicate that the UE mayuse a unique identity to prevent its request from colliding withrequests from other UEs. This scenario may be referred to as acontention-free RACH procedure.

In a contention-based RACH procedure, the UE may send a RACHtransmission to an eNB and listen for a RACH response (RAR) message. TheUE may send a message in response to the RAR message that includes acommon control channel (CCCH) payload over an uplink shared channel (ULSCH) resource identified in the RAR message. In the LTE contention-basedRACH procedure, however, no UCI is sent by the UE in response to the RARmessage. In an aspect, UCI may include CQI, PMI, RI, ACKs, and NACKs,among other information. However, because mmW communications rely onaccurate beamforming to overcome link attenuation, the reliability ofthe RACH procedure and the overall link may be improved if the messagetransmitted by the UE in response to the RAR message, which may bebeam-formed to the UE, includes beam information. For example, the beaminformation may include an identity and/or a strength of a strongestdownlink beam received at the UE from a mmW base station.

FIG. 5 is a diagram 500 of a modified RACH procedure for mmWcommunications. UEs may be scheduled for uplink transmission if itsuplink transmission timing is synchronized. For unsynchronized UEs, theRACH may be used for initial network access to achieve uplink timesynchronization for a UE that either has not yet acquired or has lostits uplink synchronization. In another aspect, an uplink-synchronized UEmay be allowed to use RACH to send a scheduling request (SR) if the UEdoes not have other uplink resources allocated in which to send the SR.

Referring to FIG. 5, a UE 502 may engage in a contention-based RACHprocedure with a base station 504 (e.g., a mmW base station). The RACHprocedure may include a message exchange involving four messages—a firstmessage 506, a second message 508, a third message 510, and a fourthmessage 512. In an aspect, the UE 502 may select an available physicalRACH (PRACH) contention-based signature (or a RACH preamble). Thesignature may be one of 64 different patterns, and if multiple UEs havethe same signature, then a collision may occur. In an aspect, a subsetof the 64 signatures/preambles may be reserved for the contention-freeRACH procedure. The UE 502 may select the signature based on the size ofthe transmission resource needed for transmitting the third message 510.The UE 502 may determine the size of the transmission resource based ona path loss and a required transmission power for the third message 510.The selected signature (or preamble) may be transmitted by the UE 502 tothe base station 504 in the first message 506. In an aspect, the firstmessage 506 may include a random access radio network temporary identity(RA-RNTI). The RA-RNTI may identify the time slot number in which thepreamble is sent and may also serve as one identifier for the UE 502.

In response to receiving the first message 506, the base station 504 maytransmit the second message 508 to the UE 502. The second message 508may be a RAR message sent via the PDSCH. The second message 508 mayprovide the identity of the detected preamble, a timing alignmentinstruction that enables the UE 502 to synchronize subsequent uplinktransmissions (e.g., a timing advance used to compensate for the roundtrip delay caused by the distance between the UE 502 and the basestation 504), and an initial uplink resource grant (e.g., PUSCH or PUCCHresource grant) for the UE 502 to transmit the third message 510 (e.g.,via the PUSCH). In an aspect, the second message 508 may include anassignment of a temporary Cell Radio Network Temporary Identifier(C-RNTI). In another aspect, the second message 508 may indicate theRA-RNTI included in the first message 506. In another aspect, the secondmessage 508 may also include a backoff indicator, which the base station504 may use to instruct the UE 502 to back off for a period of timebefore retrying a random access attempt.

In an aspect, the base station 504 may transmit the second message 508to the UE 502 using the beamforming techniques, such as those discussedin FIG. 4. When the UE 502 receives the beam-formed first message 506,the UE 502 may initiate a beam information reporting procedure. The UE502 may determine beam information associated with the second message508. For example, the second message 508 may represent a beaminformation request, and the UE 502 may measure the signal strengths ofthe various downlink beams from the base station 504 and identify thestrongest downlink beam. The UE 502 may determine one or more antennaindices at the base station 504 that are associated with the strongestdownlink beam. For example, the UE 502 may identify n beams with thestrongest beam reference signal received power (BRSRP) and report beaminformation for those n beams. The UE 502 may also determine otherbeamforming related information (or beam state information). In anotheraspect, the second message 508 may indicate a request for a number ofbeam information reports (e.g., 2 bits in which ‘00’ indicates a requestfor 1 report, ‘01’ indicates a request for 2 reports, ‘10’ indicates arequest for 4 reports, and ‘11’ indicates a request for no reports).

After determining the beam information, the UE 502 may transmit the beaminformation as a report, such as a beam state information report, in thethird message 510. The third message 510 may be a Layer 2/Layer 3message or an RRC connection request message transmitted on the PUSCH.The beam state information report may also be transmitted in the PUCCH.The third message 510 may also include a UE identifier that identifiesthe UE 502 (e.g., a random value or a temporary mobile subscriberidentity (TMSI)), an RRC connection request, a tracking area update,and/or a scheduling request. The third message may be addressed to thetemporary C-RNTI indicated in the second message 508 or include apermanent C-RNTI if the UE 502 was previously connected to the basestation 504.

After receiving the third message 510, the base station 504 may adjustone or more transmission parameters for beam forming based on the beaminformation contained in the third message 510. For example, the basestation 504 may select one or more antennas, determine transmit power onthe selected antennas, and/or choose an MCS to use for subsequenttransmission to the UE 502.

The base station 504 may transmit the fourth message 512 to the UE 502.The fourth message 512 may be a contention resolution message (e.g., ifmultiple UEs initiated the RACH procedure using the same selectedsignature). In an aspect, the fourth message 512 may be transmittedusing beamforming based on parameters that were adjusted according tothe received beam information. The fourth message 512 may be addressedto the permanent C-RNTI or the temporary C-RNTI indicated in the thirdmessage 510. If the third message 510 includes a temporary C-RNTI, thenthe fourth message 512 may echo the UE identifier indicated in the thirdmessage 510. If there is a collision, only the UE identified in thefourth message 512 may transmit HARQ feedback to the base station 504.Other UEs may understand there was a collision and may not transmit anyHARQ feedback to the base station 504.

FIG. 6A is a diagram 600 of a message (e.g., the third message 510 or anRRC connection request message) transmitted during a RACH procedure. Themessage may include a MAC header, one or more MAC control elements (MACCEs) such as a first MAC CE 604 and a second MAC CE 606, and a payload608. In an aspect, the message may correspond to the third message 510in FIG. 5, and the beam information may be contained in various portionsof the message.

In a first configuration, the beam information may be carried within thefirst MAC CE 604 (or any other MAC CE). For example, the first MAC CE604 may be defined to include one or more fields dedicated for beaminformation (e.g., an index field, a signal strength field, etc.).

In a second configuration, the beam information may be added to thepayload 608 (e.g., a CCCH payload). In LTE, the payload 608 may beechoed back by the network (e.g., the base station 504) in the fourthmessage 512. Echoing the beam information in the fourth message 512,however, may not provide any added benefit in contention-resolution. Thebase station 504 may omit the beam information from the fourth message512 or provide other control information in the fourth message 512. Inthis configuration, the beam information may be represented as one ormore bits. The bits may be concatenated with any existing bits to betransmitted in the payload 608 (e.g., tracking area update, TMSI, etc.).The combined bits may be encoded by mapping the combined bits ontomodulation symbols (e.g., BPSK, QPSK, QAM modulation) for transmissionon resource elements within one or more resource blocks such as thoseshown in FIG. 2A.

In a third configuration, the beam information may be carried in themessage as UCI, similar to CQI reports, buffer status information (BSI)reports, and basic rate information (BRI) reports. The UCI may bemultiplexed with the payload 608. Current RACH procedure does not allowfor multiplexing UCI with UL-SCH payload in the third message 510.However, such signaling may be invoked for mmW communications to improvebeamforming performance. In an aspect, a resource block 650 (or anyother number of resource blocks), as shown in FIG. 6B, may be allocatedto the UE 502 for transmitting the third message 510 based on the secondmessage 508. The payload bits may be encoded by mapping the payload bitsonto a first set of modulation symbols. The bits corresponding to thebeam information may be separately encoded onto a second set ofmodulation symbols. To determine how many resource elements in theresource block 650 to use for transmitting the beam information versusthe payload, the UE 502 may determine a beta offset value β_(offset),which may correspond to a ratio of resource elements that may be usedfor transmitting the beam information versus the resource elements thatmay be used for transmitting the payload (or vice versa). By indicatinga ratio of resource elements for reporting beam information, the betaoffset value may represent a request for a beam information (or a beamstate information) report. Referring to FIG. 6B, using the beta offsetvalue, the UE 502 may determine a first set of resources 652 to use fortransmitting the first set of modulation symbols corresponding to thepayload 608 and a second set of resources 654 for transmitting thesecond set of modulation symbols corresponding to the beam informationsuch that the payload 608 and the UCI are multiplexed together withinthe resource block 650. FIG. 6B displays one configuration formultiplexing UCI with the payload; in particular, one or more OFDMsymbols are allocated for UCI and other OFDM symbols are allocated forpayload. Other configurations may also be used. For example, within anOFDM symbol, some subcarriers or tones may be allocated for transmittingUCI while other subcarriers within the same OFDM symbol may be allocatedfor transmitting payload.

The UE 502 may determine the beta offset value in a number of differentways. In one aspect, the beta offset value may be a fixed, default valueused by all UEs when UEs have beam information to transmit. In anotheraspect, the beta offset value may be a function of one or moreparameters transmitted in the PBCH (e.g., a system frame number, anumber of transmit antennas used by the base station 504, systembandwidth, etc.). In another aspect, the beta offset value may bereceived from the network or from the base station 504 within the secondmessage 508, for example. In this aspect, the beta offset value may beoptional within the second message 508. A missing beta offset value mayindicate that the UE 502 is to use a default value or may indicate thatthe UE 502 is not to transmit any beam information.

In another aspect, in a contention-free RACH procedure, if the basestation 504 orders the UE 502 (via a message transmitted in the PDCCH)to perform uplink timing synchronization, the UE 502 may already be RRCconnected to the base station 504, and therefore, may already have thebeta offset value. In another aspect, during a handover from a sourcebase station to a target base station, a handover message from the UE502 to the target base station (or vice versa) may signal the betaoffset value. In another aspect, during handover, the UE 504 may use theexisting beta offset value prior to handover, and the source basestation may signal the beta offset value to the target base station.

FIG. 7 is a flowchart 700 of a method of wireless communication. Themethod may be performed by a UE (e.g., the UE 502, the apparatus802/802′).

At 702, the UE may receive a beam-formed message from a base stationduring a RACH procedure. For example, referring to FIG. 5, the UE may bethe UE 502, and the base station may be the base station 504. The UE 502may receive the second message 508 (the beam-formed message) from thebase station 504 during a RACH procedure. As previously noted, thesecond message 508 may also be a beam state information request,requesting the UE 502 to obtain beam state information.

At 704, the UE may determine beam information based on the receivedbeam-formed message during the RACH procedure. For example, referring toFIG. 5, the UE 502 may determine beam information based on the secondmessage 508 received from the base station 504. The UE 502 may measurethe received signal strength of the various downlink beams from the basestation 504. The UE 502 may identify a beam received from the basestation 504 (e.g., identify the transmit antenna index) that has thestrongest signal strength. The beam information may include the indexidentifying the strongest received beam (e.g., the index may correspondto the antenna at the base station 504) and the signal strength of thestrongest received beam.

In one configuration, at 706, the UE 502 may multiplex the determinedbeam information as UCI with a payload for transmission during the RACHprocedure. The UE 502 may multiplex the determined beam information by,at 708, determining an offset value for multiplexing the determined beaminformation with the payload. The offset value may indicate a ratio ofUCI modulation symbols to payload modulation symbols. At 710, the UE 502may multiplex the determined beam information based on the determinedoffset value. For example, referring to FIGS. 5, 6A, and 6B, the UE 502may determine the offset value by receiving the offset value from thebase station 504 in the second message 508. The UE 504 may multiplex thebeam information with the payload 608 data for transmission in the thirdmessage 510 based on the beta offset value.

At 712, the UE may transmit a message to the base station during theRACH procedure that includes the determined beam information. Forexample, referring to FIG. 5, the UE 502 may transmit the third message510 to the base station 504 during the RACH procedure, and the thirdmessage 510 may include the determined beam information. In one example,the beam information may be multiplexed with the payload 608 of thethird message 510 as described at 706, 708, and 710. In another example,the beam information may be included in the first MAC CE 604 of thethird message 510. In yet another example, the beam information may beencoded with the payload 608 of the third message 510.

FIG. 8 is a conceptual data flow diagram 800 illustrating the data flowbetween different means/components in an exemplary apparatus 802. Theapparatus may be a UE. The apparatus includes a reception component 804,a detection component 806, an encoding component 808, and a transmissioncomponent 810. The reception component 804 may be configured to receivea beam-formed message from a base station 850 during a RACH procedure.The detection component 806 may be configured to determine beaminformation based on the received beam-formed message during the RACHprocedure. The transmission component 810 may be configured to transmita message to the base station 850 during the RACH procedure thatincludes the determined beam information. In one aspect, the beaminformation may include an index identifying a strongest received beamat the apparatus or a signal strength of the strongest received beam atthe apparatus. In another aspect, the determined beam information may beincluded in a MAC-CE of the message. In another aspect, the determinedbeam information may be included in a payload of the message. In oneconfiguration, the encoding component 808 may be configured to multiplexthe determined beam information as UCI with a payload of the message fortransmission during the RACH procedure. The encoding component 808 maybe configured to multiplex by determining an offset value formultiplexing the determined beam information with the payload, in whichthe offset value indicates a ratio of UCI modulation symbols to payloadmodulation symbols to be transmitted in the message, and to multiplexthe determined beam information based on the determined offset value. Inan aspect, the offset value may be a default value, based on physicalbroadcast channel parameters, or received from a network. In anotheraspect, the offset value may be received from the base station 850 in aRACH response message based on a PRACH transmission by the UE.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowcharts of FIG. 7. Assuch, each block in the aforementioned flowcharts of FIG. 7 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 9 is a diagram 900 illustrating an example of a hardwareimplementation for an apparatus 802′ employing a processing system 914.The processing system 914 may be implemented with a bus architecture,represented generally by the bus 924. The bus 924 may include any numberof interconnecting buses and bridges depending on the specificapplication of the processing system 914 and the overall designconstraints. The bus 924 links together various circuits including oneor more processors and/or hardware components, represented by theprocessor 904, the components 804, 806, 808, and the computer-readablemedium/memory 906. The bus 924 may also link various other circuits suchas timing sources, peripherals, voltage regulators, and power managementcircuits, which are well known in the art, and therefore, will not bedescribed any further.

The processing system 914 may be coupled to a transceiver 910. Thetransceiver 910 is coupled to one or more antennas 920. The transceiver910 provides a means for communicating with various other apparatus overa transmission medium. The transceiver 910 receives a signal from theone or more antennas 920, extracts information from the received signal,and provides the extracted information to the processing system 914,specifically the reception component 804. In addition, the transceiver910 receives information from the processing system 914, specificallythe transmission component 810, and based on the received information,generates a signal to be applied to the one or more antennas 920. Theprocessing system 914 includes a processor 904 coupled to acomputer-readable medium/memory 906. The processor 904 is responsiblefor general processing, including the execution of software stored onthe computer-readable medium/memory 906. The software, when executed bythe processor 904, causes the processing system 914 to perform thevarious functions described supra for any particular apparatus. Thecomputer-readable medium/memory 906 may also be used for storing datathat is manipulated by the processor 904 when executing software. Theprocessing system 914 further includes at least one of the components804, 806, 808. The components may be software components running in theprocessor 904, resident/stored in the computer readable medium/memory906, one or more hardware components coupled to the processor 904, orsome combination thereof. The processing system 914 may be a componentof the UE 350 and may include the memory 360 and/or at least one of theTX processor 368, the RX processor 356, and the controller/processor359.

In one configuration, the apparatus 802/802′ for wireless communicationincludes means for receiving a beam-formed message from a base stationduring a RACH procedure. The apparatus may include means for determiningbeam information based on the received beam-formed message during theRACH procedure. The apparatus may include means for transmitting amessage to the base station during the RACH procedure that includes thedetermined beam information. In one aspect, the beam information mayinclude an index identifying a strongest received beam at the apparatusor a signal strength of the strongest received beam at the apparatus. Inanother aspect, the determined beam information is included in a MAC-CEof the message. In another aspect, the determined beam information maybe included in a payload of the message. In one configuration, theapparatus may include means for multiplexing the determined beaminformation as UCI with a payload of the message for transmission duringthe RACH procedure. In an aspect, the means for multiplexing may beconfigured to determine an offset value for multiplexing the determinedbeam information with the payload, in which the offset value indicates aratio of UCI modulation symbols to payload modulation symbols to betransmitted in the message, and to multiplex the determined beaminformation based on the determined offset value. In an aspect, theoffset value may be a default value, based on physical broadcast channelparameters, or received from a network. In another aspect, the offsetvalue may be received from the base station in a RACH response messagebased on a PRACH transmission by the UE. The aforementioned means may beone or more of the aforementioned components of the apparatus 802 and/orthe processing system 914 of the apparatus 802′ configured to performthe functions recited by the aforementioned means. As described supra,the processing system 914 may include the TX Processor 368, the RXProcessor 356, and the controller/processor 359. As such, in oneconfiguration, the aforementioned means may be the TX Processor 368, theRX Processor 356, and the controller/processor 359 configured to performthe functions recited by the aforementioned means.

The teachings, methods, techniques, and principles described herein arenot limited to mmW networks and communications but are also applicableto other communication networks that utilize beamforming.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication by a userequipment (UE), comprising: receiving a message from a base stationduring a random access channel (RACH) procedure; determining beaminformation based on the received message during the RACH procedure; andtransmitting a second message to the base station during the RACHprocedure that includes the determined beam information, wherein themessage, received during the RACH procedure, comprises a valueindicating a request for beam information during the RACH procedure, andwherein the second message is transmitted based on the request for beaminformation.
 2. The method of claim 1, wherein the received message isbeam-formed and the beam information comprises an index identifying astrongest received beam at the UE or a signal strength of the strongestreceived beam at the UE on which the beam-formed message was received.3. The method of claim 1, wherein the determined beam information isincluded in a medium access control (MAC) control element (CE) (MAC-CE)of the second message.
 4. The method of claim 1, wherein the determinedbeam information is included in a payload of the second message.
 5. Themethod of claim 1, further comprising multiplexing the determined beaminformation as uplink control information (UCI) with a payload of thesecond message for transmission during the RACH procedure.
 6. The methodof claim 5, wherein the multiplexing comprises: determining an offsetvalue for multiplexing the determined beam information with the payload,the offset value indicating a ratio of UCI modulation symbols to payloadmodulation symbols to be transmitted in the second message; andmultiplexing the determined beam information based on the determinedoffset value.
 7. The method of claim 6, wherein the offset value is adefault value, based on physical broadcast channel parameters, orreceived from a network.
 8. The method of claim 7, wherein the offsetvalue is received from the base station in a RACH response message basedon a physical RACH (PRACH) transmission by the UE.
 9. The method ofclaim 1, wherein the message is a random access response (RAR) messageindicating a resource on a physical uplink shared channel (PUSCH) fortransmitting the beam information, and wherein the beam information istransmitted on the resource indicated in the RAR message.
 10. Anapparatus for wireless communication, comprising: means for receiving amessage from a base station during a random access channel (RACH)procedure; means for determining beam information based on the receivedmessage during the RACH procedure; and means for transmitting a secondmessage to the base station during the RACH procedure that includes thedetermined beam information, wherein the message, received during theRACH procedure, comprises a value indicating a request for beaminformation during the RACH procedure, and wherein the second message istransmitted based on the request for beam information.
 11. The apparatusof claim 10, wherein the received message is beam-formed and the beaminformation comprises an index identifying a strongest received beam atthe apparatus or a signal strength of the strongest received beam at theapparatus.
 12. The apparatus of claim 10, wherein the determined beaminformation is included in a medium access control (MAC) control element(CE) (MAC-CE) of the second message.
 13. The apparatus of claim 10,wherein the determined beam information is included in a payload of thesecond message.
 14. The apparatus of claim 10, further comprising meansfor multiplexing the determined beam information as uplink controlinformation (UCI) with a payload of the second message for transmissionduring the RACH procedure.
 15. The apparatus of claim 14, wherein themeans for multiplexing is configured to: determine an offset value formultiplexing the determined beam information with the payload, theoffset value indicating a ratio of UCI modulation symbols to payloadmodulation symbols to be transmitted in the second message; andmultiplex the determined beam information based on the determined offsetvalue.
 16. The apparatus of claim 15, wherein the offset value is adefault value, based on physical broadcast channel parameters, orreceived from a network.
 17. The apparatus of claim 16, wherein theoffset value is received from the base station in a RACH responsemessage based on a physical RACH (PRACH) transmission by the apparatus.18. The apparatus of claim 10, wherein the message is a random accessresponse (RAR) message indicating a resource on a physical uplink sharedchannel (PUSCH) for transmitting the beam information, and wherein thebeam information is transmitted on the resource indicated in the RARmessage.
 19. An apparatus for wireless communication, comprising: amemory; and at least one processor coupled to the memory and configuredto: receive a message from a base station during a random access channel(RACH) procedure; determine beam information based on the receivedmessage during the RACH procedure; and transmit a second message to thebase station during the RACH procedure that includes the determined beaminformation, wherein the message, received during the RACH procedure,comprises a value indicating a request for beam information during theRACH procedure, and wherein the second message is transmitted based onthe request for beam information.
 20. The apparatus of claim 19, whereinthe received message is beam-formed and the beam information comprisesan index identifying a strongest received beam at the UE or a signalstrength of the strongest received beam at the UE.
 21. The apparatus ofclaim 19, wherein the determined beam information is included in amedium access control (MAC) control element (CE) (MAC-CE) of the secondmessage.
 22. The apparatus of claim 19, wherein the determined beaminformation is included in a payload of the second message.
 23. Theapparatus of claim 19, wherein the at least one processor is furtherconfigured to multiplex the determined beam information as uplinkcontrol information (UCI) with a payload of the second message fortransmission during the RACH procedure.
 24. The apparatus of claim 23,wherein the at least one processor is configured to multiplex by:determining an offset value for multiplexing the determined beaminformation with the payload, the offset value indicating a ratio of UCImodulation symbols to payload modulation symbols to be transmitted inthe second message; and multiplexing the determined beam informationbased on the determined offset value.
 25. The apparatus of claim 24,wherein the offset value is a default value, based on physical broadcastchannel parameters, or received from a network.
 26. The apparatus ofclaim 25, wherein the offset value is received from the base station ina RACH response message based on a physical RACH (PRACH) transmission bythe apparatus.
 27. The apparatus of claim 19, wherein the message is arandom access response (RAR) message indicating a resource on a physicaluplink shared channel (PUSCH) for transmitting the beam information, andwherein the beam information is transmitted on the resource indicated inthe RAR message.
 28. A computer-readable medium of a user equipment (UE)storing computer executable code, comprising code to: receive a messagefrom a base station during a random access channel (RACH) procedure;determine beam information based on the received message during the RACHprocedure; and transmit a second message to the base station during theRACH procedure that includes the determined beam information, whereinthe message, received during the RACH procedure, comprises a valueindicating a request for beam information during the RACH procedure, andwherein the second message is transmitted based on the request for beaminformation.
 29. A method of wireless communication by a user equipment(UE), comprising: receiving an uplink resource grant including an offsetvalue from a base station; determining, based on the offset value,resource elements of a resource block for transmitting uplink controlinformation (UCI) in an uplink data channel, wherein the offset valueindicates a ratio of the resource elements of the resource block fortransmitting the UCI to resource elements of the resource block fortransmitting a data payload of an uplink message in the uplink datachannel; and transmitting the UCI in the uplink data channel on theresource elements.
 30. The method of claim 29, further comprising:multiplexing the UCI with the data payload of the uplink message basedon the offset value for transmission in the uplink data channel.
 31. Themethod of claim 29, wherein the UCI includes at least one of channelquality indicator (CQI), a precoding matrix indicator (PMI), a rankindicator (RI), an acknowledgment (ACK) feedback, a negative ACK (HACK)feedback, or beam information associated with a downlink beam.
 32. Themethod of claim 31, wherein the beam information includes an indexidentifying a strongest received beam at the UE or a signal strength ofthe strongest received beam at the UE on which a downlink message wasreceived in a beam-formed manner.
 33. The method of claim 32, whereinthe uplink resource grant is received in the downlink message.
 34. Themethod of claim 32, wherein the downlink message is a RACH responsemessage received in response to a physical RACH (PRACH) transmission bythe UE.
 35. The method of claim 34, wherein the UCI is transmitted inresponse to the RACH response message.
 36. The method of claim 29,wherein the uplink resource grant is a physical uplink shared channel(PUSCH) resource grant, the uplink data channel being the PUSCH.